Air pollution exposure, cause-specific deaths and hospitalizations in a highly polluted Italian region

Background. The Lombardy region in northern Italy ranks among the most air polluted areas of Europe. Previous studies showed air pollution short-term effects on all-cause mortality. We examine here the effects of particulate matter with aerodynamic diameter ≤10 μm (PM₁₀) and nitrogen dioxide (NO₂) exposure on deaths and hospitalizations from specific causes, including cardiac, cerebrovascular and respiratory diseases.

Methods. We considered air pollution, mortality and hospitalization data for a non-opportunistic sample of 18 highly polluted and most densely populated areas of the region in the years 2003-2006. We obtained area-specific effect estimates for PM₁₀ and NO₂ from a Poisson regression model on the daily number of total deaths or cause-specific hospitalizations and then combined them in a Bayesian random-effects meta-analysis. For cause-specific mortality, we applied a case-crossover analysis. Age- and season-specific analyses were also performed. Effect estimates were expressed as percent variation in mortality or hospitalizations associated with a 10 μg/m³ increase in PM₁₀ or NO₂ concentration.

Results. Natural mortality was positively associated with both pollutants (0.30%, 90% Credibility Interval [CrI]: -0.31; 0.78 for PM₁₀; 0.70%, 90%CrI: 0.10; 1.27 for NO₂). Cardiovascular deaths showed a higher percent variation in association with NO₂ (1.12%, 90% Confidence Interval [CI]: 0.14; 2.11), while the percent variation for respiratory mortality was highest in association with PM₁₀ (1.64%, 90%CI: 0.35; 2.93). The effect of both pollutants was more evident in the summer season. Air pollution was also associated to hospitalizations, the highest variations being 0.77% (90%CrI: 0.22; 1.43) for PM₁₀ and respiratory diseases, and 1.70% (90%CrI: 0.39; 2.84) for NO₂ and cerebrovascular diseases. The effect of PM₁₀ on respiratory hospital admissions appeared to increase with age. For both pollutants, effects on cerebrovascular hospitalizations were more evident in subjects aged less than 75 years.

Conclusions. Our study provided a sound characterization of air pollution exposure and its potential effects on human health in the most polluted, and also most populated and productive, Italian region, further documenting the need for effective public health policies.